The technical field of this invention is the deployment of an occupant restraint in a motor vehicle during a vehicle crash event.
Occupant restraint deployment systems have generally relied on a crash sensing and discrimination apparatus in a passenger area of the vehicle, with the addition, in some cases, of satellite sensors in outboard areas of the vehicle such as the frontal crush space and/or vehicle side doors. The satellite sensors have tended to be electromechanical acceleration or velocity responsive switches. The satellite sensors were designed for the specific application, with little flexibility in design or function. Generally speaking, such satellite sensors designed for one location or function were not usable in a different location or function. But recent developments in the field of occupant restraint deployment for motor vehicles call for an advance in the capabilities of xe2x80x9csmartxe2x80x9d satellite sensors, in which signal processing for crash severity discrimination is provided in satellite sensors in the frontal crush space for discrimination of frontal restraint deployment and/or in a vehicle side door for discrimination of side restraint deployment. With the multiplicity of installed sensors, it is desirable to provide a smart satellite sensor that can be used in a variety of vehicle locations and/or functions with minimal change.
An oscillation measure was developed to address front impact specific criteria. This frontal oscillation measure, described in U.S. Pat. No. 5,483,449, issued Jan. 9, 1996 to Caruso et al, integrates the absolute value of a jerk measure obtained from the derivative of a sensed acceleration signal in a frontal impact sensing area. This oscillation measure has proven effective in helping to distinguish deployment desirable crash events for a frontal restraint, but it has not been equally successful in discriminating such events for a side restraint, since the vehicle side door environment of the satellite sensor is subject to significant accelerations due to door slams and other misuse events in which occupant restraint deployment is not desired.
Another oscillation measure was developed with unique application to side restraint deployment. This side oscillation measure integrates the non-absolute, signed value of the jerk measure obtained from the derivative of a sensed acceleration signal in a side impact sensing area. In this oscillation measure, negative accelerations found frequently in side misuse events are subtracted from, rather than added to, the total side oscillation measure. But the difference in the oscillation measure has meant different satellite sensors for frontal and side impact crash discrimination.
The object of this invention is to provide a mechanism for discriminating crash severity in a system for controlling the deployment of an occupant restraint that is equally applicable to front and side restraints with minimal change. The object is realized in an apparatus for controlling deployment of an occupant restraint in a motor vehicle crash. The apparatus receives a sensed acceleration signal, derives an oscillation value from consecutive sampled values of the received acceleration signal by a selected one of two alternative methods and derives an occupant restraint deployment signal using the derived oscillation value. The apparatus stores code for both of the methods for deriving the oscillation value and selects the code and method in accordance with the stored datum. Thus the apparatus may be made virtually identically for different sensor applications in a vehicle, such a frontal and side applications, with the stored datum, set during manufacture, determining the actual sensor operation. The apparatus has particular application to alternative frontal and side applications, wherein the use of the first method may be more appropriate for discrimination of frontal crashes and the use of the second method may be more appropriate for discrimination of side crashes.